The present invention relates to a biopesticidal composition for controlling insects (e.g., pecan weevils, the diaprepes root weevil, fall armyworm, fire ants), containing an agriculturally acceptable carrier and an effective insect (e.g., pecan weevils, the diaprepes root weevil, fall armyworm, fire ants) biopesticidal amount of at least one fungus selected from Beauveria bassiana having the identifying characteristics of Beauveria bassiana NRRL 30593, Metarhizium anisopliae having the identifying characteristics of Metarhizium anisopliae NRRL 30594, Beauveria bassiana having the identifying characteristics of Beauveria bassiana NRRL 30601, Beauveria bassiana having the identifying characteristics of Beauveria bassiana NRRL 30600, or mixtures thereof. The present invention also relates to a method for controlling insects (e.g., pecan weevils, the diaprepes root weevil, fall armyworm, fire ants) involving applying an effective insect biopesticidal amount of the above composition to the insects or to the plants, areas or substrates infested with the insects.
Insect pests are a major problem for agriculture. For example, the pecan weevil, Curculio caryae (Horn), is a major pest of pecans throughout the Southeast United States (Mizell, R. F., Risk rating: A fruitful approach to management of the pecan weevil, pp. 69-78, In W. W. Neel [ed], Pecan weevil: research perspective, 1985, Quail Ridge Press, Brandon, Miss.). The insects have a two or three-year life-cycle (Harris, M. K., Pecan phenology and pecan weevil biology and management, pp. 51-58, In W. W. Neel [ed], Pecan weevil: research perspective, 1985, Quail Ridge Press, Brandon, Miss.). Adults emerge from soil in late July-August and then feed on and oviposit in the nuts. Larvae develop within the nut and fourth instars drop to the soil where they burrow to a depth of 8-25 cm. The following year approximately 90% of the larvae pupate and spend the next nine months in the soil as adults; the remaining 10% of the population spend two years in the soil as larvae emerging as adults in the third year.
Control recommendations for the pecan weevil currently consist solely of applications of chemical insecticides (e.g., carbaryl) to the tree canopy to suppress adults (Ellis, H. C., et al., Georgia pecan pest management guide, University of Georgia Cooperative Extension Service Bulletin No. 841 (2000); Harris, M. K., Pecan weevil management considerations, pp. 66-73, In B. McCraw, E. H. Dean, and B. W. Wood [eds.], Pecan industry: current situation and future challenges, third national pecan workshop proceedings, 1999, U.S. Department of Agriculture, Agricultural Research Service). Late season applications of carbaryl, however, can result in resurgence of damaging aphid populations because carbaryl suppresses certain aphid predators (e.g., coccinellids) but does not suppress the pecan aphid complex (Dutcher, J. D., and J. A. Payne, The impact of pecan weevil control strategies on non-target arthropods, pp. 39-50, In W. W. Neel [ed], Pecan weevil: research perspective, 1985, Quail Ridge Press, Brandon, Miss.). Due to the problems associated with aphid resurgence, as well as other environmental and regulatory concerns, research on developing alternative control strategies is warranted. Microbial control (i.e., use of entomopathogenic viruses, bacteria, protozoa, fungi, or nematodes) is one of the potential alternatives to current chemical insecticides.
Among entomopathogens of C. caryae studied thus far, certain Hyphomycetes fungi (i.e., Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin) have shown the most promise as microbial control agents (Fuxa, J. R., et al., Pathogens and microbial control of north American forest insect pests, Forest Health Technology Enterprise Team, 1998, USDA Forest Service, Morgantwown, W. Va.; Gottwald, T. R., and W. L. Tedders, Suppression of pecan weevil (Coleoptera: Curculionidae) populations with entomopathogenic fungi, Environ. Entomol., 12: 471-474 (1983); Sikorowski, P. P., Pecan weevil pathology, pp. 87-101, In W. W. Neel [ed] Pecan weevil: Research perspective, 1985, Quail Ridge Press, Brandon, Miss.). Fungi in the class Hyphomycetes generally invade the insect host through the cuticle, replicate within the host's hemocoel, and form external conidiophores to disperse their spores (Tanada Y., and H. K. Kaya., Insect Pathology, 1993, Academic Press, San Diego, Calif.). The fungi B. bassiana and M. anispoliae are pathogenic to a wide variety of insects including a number of curculionid or other coleopteran pests (Tanada Y., and H. K. Kaya., Insect Pathology, 1993, Academic Press, San Diego, Calif.). Due to susceptibility to environmental extremes (e.g., low relative humidity, ultraviolet light, temperature), fungi are most successful when applied to soil or other “protected” environments (Fuxa, J. R., and Y. Tanada [eds.], Epizootiology of insect diseases, 1987, John Wiley and Sons, New York, N.Y.). Microbial control of C. caryae with these agents is most likely to be successful when fungi are applied to soil as a barrier treatment when larvae are dropping from nuts or when adults are emerging (Sikorowski, P. P., Pecan weevil pathology, pp. 87-101, In W. W. Neel [ed] Pecan weevil: Research perspective, 1985, Quail Ridge Press, Brandon, Miss.).
Some promising results have been reported in suppressing C. caryae with fungi (e.g.,>60% suppression) (Gottwald, T. R., and W. L. Tedders, Suppression of pecan weevil (Coleoptera: Curculionidae) populations with entomopathogenic fungi, Environ. Entomol., 12: 471-474 (1983); Tedders, W. L., et al., Pecan weevil: suppression of larvae with the fungi Metarhizium anisopliae and Beauveria bassiana and the nematode Neoaplectana dutkyi, J. Econ. Entomol., 66: 723-725 (1973)). However, other laboratory and field experiments indicate a lack of consistency (i.e., less than 35% suppression) (Harrison, R. D., et al., Relative susceptibility of pecan weevil fourth instars and adults to selected isolates of Beauveria bassiana, Biological Control, 3: 34-38 (1993)). Virulence can depend substantially on the strain or species of the particular entomopathogen being used (Shapiro-Ilan D. I., et al., Factors affecting commercial success: case studies in cotton, turf, and citrus, In R. Gaugler, [ed.] Entomopathogenic Nematology, CABI, In press; Tanada Y., and H. K. Kaya, Insect Pathology, 1993, Academic Press, San Diego, Calif.). Discovery of new strains or species of fungi may lead to enhanced potential for microbial control since susceptibility of C. caryae varies among species or strains of entomopathogenic fungi (Harrison, R. D., et al., Relative susceptibility of pecan weevil fourth instars and adults to selected isolates of Beauveria bassiana, Biological Control, 3: 34-38 (1993)).